Semi-bright nickel plating



United States Patent C ABSTRACT OF THE DISCLOSURE A semi-bright nickel plate is obtained by passing current from an anode to a metal cathode in an aqueous nickel plating solution which contains as cooperating semi-bright additives an aromatic aldehyde in combination with an aliphatic aldehyde.

This invention relates to the electroplating of nickel. More particularly, this invention relates to the electroplating of semi-bright nickel which is characterized by a uniformly fine-grained structure and excellent ductility.

As is known to those skilled-in-the-art, semi-bright nickel may be deposited as an underlying layer for bright nickel. Numerous defects and shortcomings of such deposits have been observed in commercial operation. Thus, the accumulation of decomposition products may adversely affect ductility; non-uniform grain size of the deposit may result in the need for a thicker bright nickel deposit in order to obtain maximum luster over all significant plated areas. Moreover, the formation of resinous or polymeric products resulting from decomposition of the additives may cause a number of surface defects.

It is an object of this invention to provide a novel process for electrodepositing semi-bright nickel plate. A further object of this invention is to provide a novel process and composition useful for the preparation of semi-bright nickel plate. Other objects will be apparent to those skilled-in-the-art upon inspection of the following detailed description of the invention.

In accordance with certain of its aspects, the novel process of this invention for electrodepositing a semibright nickel plate onto a basis metal may comprise passing current from an anode to a metal cathode in an aqueous acidic nickel plating solution containing at least one nickel compound providing nickel ions for electrode'positing nickel, and including as cooperating semibright additives an aromatic aldehyde in combination with an aliphatic aldehyde in said aqueous acidic nickel plating solution.

The basis metal on which the semi-bright deposits of this invention may be applied may include ferrous metals such as steel; copper, including its alloys such as brass, bronze, etc.; zinc, particularly in the form of die castings which may bear a plate of copper; thin metal coatings, e.g. of silver or copper on a non-conductive or conductive article, which may be applied by chemical reductive techniques (such as electroless metal plating).

The novel baths of this invention may typically include Watts-type baths, sulfamate-type baths, mixed Watts-sulfamate-type baths, chloride-free sulfate baths, chloridefree sulfamate baths, chloride-free mixed sulfate-sulfamate baths, etc.

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A typical Watts bath which may be used in practice of this invention may include the following components in aqueous solution, all values being in grams per liter (g./l.) except for the pH which is electrometric:

TABLE I Component Minimum Maximum Preferred Nickel sulfate heptahydrate 200 500 300 Nickel chloride hexahydrate 7 45 Boric acid 35 55 45 pH 3 5 4 A typical sulfamate-type bath which may be used in practice of this invention may include the following components:

TABLE II Component Minimum Maximum Preferred Nickel sulfamate 330 600 375 Nickel chloride hexahydrate 15 60 45 Boric acid 35 55 45 pH 3 5 4 A typical mixed Watts-sulfamate-type bath which may be used in the practice of the invention may include the A typical fluoborate-type bath which may be used in the practice of the invention may include the following components:

TABLE IV Component Minimum Maximum Preferred- Nickel fluob orate 250 400 300 Nickel chloride hex-ahydrate 45 6O 50 B oric acid, 15 30 20 pH 2 4 3 A typical chloride-free sulfate bath which may be used in the practice of the invention may include the following components:

TABLE V Comp onent Minimum Maximum Preferred Nickel sulfate heptahydrate. 300 500 400 Boric acid 35 55 45 pH 3 5 4 A typical chloride-free sulfamate bath which may be used in the practice of the invention may include the following components:

TABLE VI Component Minimum Maximum Preferred Nickel sulfamate 300 400 350 35 55 45 3 A typical chloride-free mixed sulfate-sulfamate bath which may be used in the practice of the invention may include the following components:

TABLE VII Component Minimum Maximum Preferred Nickel sulfate heptahydrate 100 250 150 Nickel sulfamate 165 300 190 B oric acid 35 55 45 pH a 3 5 4 In accordance with a specific embodiment of this invention, there may be present in the nickel plating baths as semi-bright additive, an aromatic aldehyde and an aliphatic aldehyde. This additive composition may cooperate with or be compatible with the nickel plating bath.

An aromatic aldehyde is defined as a compound which contains an aldehyde group and a benzene nucleus in the molecule.

The benzene nucleus of the aromatic aldehyde may be further substituted by ring structures which may be condensed to adjacent carbon positions on the benzene nucleus. These condensed ring structures may be carboxylic or heterocyclic. Thus typical aromatic aldehydes or these types may include, e.g. l-naphthaldehyde, 2- naphthaldehyde, p-cyclohexylbenzaldehyde, piperonal, etc. The preferred aromatic aldehydes may be: cinnamaldehyde; piperonal (also known as heliotropine) including substituted piperonals wherein the substituents are directly bonded to carbon atoms of the aromatic nucleus; and benzaldehyde or substituted 'benzaldehydes wherein the substituents are bonded directly to the carbon atoms of the benzene nucleus.

The benzene nucleus of the aromatic aldehydes or the rings which are condensed to the benzene nucleus, when present, may in addition bear inert non-reactive or solubili' zing substituents including hydrocarbon groups, ether groups, carboxy groups, ester groups, hydroxy-containing groups, halogens, etc.

Typical hydrocarbon radicals which may be present in the aromatic aldehyde compound may include alkyl, alkenyl, cycloalkyl, aralkyl, aryl, and alkaryl, including such radicals when inertly substituted. When the hydrocarbon radical is alkyl, it may typically be straight chain alkyl or branched alkyl, including methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-amyl, neopentyl, isoamyl, n-hexyl, isohexyl, heptyls, octyls, decyls, dodecyls, tetradecyl, octadecyl, etc. Preferred alkyl includes lower alkyl, i.e. having less than about 8 carbon atoms, i.e. octyls and lower. When the hydrocarbon radical is alkenyl, it may typically be vinyl, allyl, l-propenyl, methallyl, buten-l-yl, buten-Z-yl, buten-3-yl, etc. When the hydrocarbon radical is cycloalkyl, it may typically be cyclopentyl, cyclohexyl, etc. When the hydrocarbon radical is aralkyl, it may typically be 'benzyl, ,B-phenylethyl, 'y-phenylpropyl, B-phenylpropyl, etc. When the hydrocarbon radical is aryl, it may typically be phenyl, naphthyl, etc. When the hydrocarbon radical is alkaryl, it may typically be tolyl, xylyl, p-ethylphenyl, etc. The hydrocarbon radical substituent may also be inertly substituted, e.g. may bear a non-reactive substituent such as alkyl, aryl, cycloalkyl, aralkyl, alkaryl, alkenyl, ether, ester,.etc. Typical substituted alkyls include 2-ethoxyethyl, carboethoxymethyl, etc. Substituted alkenyls include "yphenylpropenyl, etc. Substituted cycloalkyls include 4- methylcyclohexyl, etc. Inertly substituted aryl includes chlorophenyl, anisyl, biphenyl, etc. Inertly substituted aralkyl includes p-phenylbenzyl, p=methylbenzyl, etc,

The aldehyde group CHO of the aromatic aldehyde may be bonded directly to the benzene ring, as in benzaldehyde; or it may be positioned elsewhere in the molecule of the aromatic aldehyde, as in cinnamaldehyde.

Typical aromatic aldehydes may include piperonal; benzaldehyde; o-hydroxy benzaldehyde; p-hydroxy benzaldehyde; vanillin (i.e. 4hydroxy-3-methoxy benzaldehyde); isovanillin (i.e. 3-hydroxy-4-methoxy benzaldehyde); veretraldehyde (i.e. 3,4-di-methoxy benzaldehyde); vanillin ethyl ether (i.e. 3-ethoxy-4-hydroxy benzaldehyde); o-methoxy benzaldehyde; p-methoxy benzaldehyde; 2,3 di-methoxy benzaldehyde; o-phthaldehyde; mphthaldehyde; and terephthaldehyde. Preferred aldehydes of this type may be o-methoxy benzaldehyde; veratraldehyde; piperonal; vanillin; and benzaldehyde.

Other typical aldehydes may include phenylacetaldehyde; Z-phenylpropionaldehyde; 3-phenylpropionaldehyde; 2 phenylbutyraldehyde; 3 phenylbutyraldehyde; 4-phenylbutyraldehyde; and cinnamaldehyde. A preferred aldehyde of this type may be cinnamaldehyde.

Highly preferred constituents of the semi-bright additive discussed above may be the aromatic aldehydes and particularly benzaldehyde; aromatic aldehydes substituted by at least one solubilizing group, e.g. o-hydroxy benzaldehyde; p-hydroxy benzaldehyde; vanillin (i.e. 4- hydroxy-3-methoxy benzaldehyde); isovanillin (i.e. 3-hydroxy-4-methoxy benzaldehyde); veretraldehyde (i.e. 3,.4-di-methoxy benzaldehyde); vanillin ethyl ether (i.e. 3-ethoxy-4-hydroxy benzaldehyde); o-methoxy benzaldehyde; p-methoxy benzaldehyde; 2,3-di-methoxy benzaldehyde; o-phthaldehyde; and terephthaldehyde; aromatic aldehydes in which a benzene nucleus is condensed in adjacent positions with a carbocyclic ring, e.g. Z-hydroxyl-naphthaldehyde; 1-hydroxy-4-naphthaldehyde; l-rnethoxy-4-naphthaldehyde; naphth-di-aldehyde-1,2; naphthaldehyde2,4; 1-hydroxy-Z-naphthaldehyde; l-methoxy- Z-naphthaldehyde, 1-hydroxy-3-naphthaldehyde; l-methoxy-8-naphthaldehyde; Z-methoxy-8-naphthaldehyde; 3- methoxy-8-naphthaldehyde; 4-methoxy-8-naphthaldehyde; and aromatic aldehydes in which a benzene nucleus is condensed in adjacent positions with a heterocyclic group, e.g. a dioxymethylene group, as in piperonal. The above types of highly preferred aldehydes may also bear inert or non-reactive substituents such as halogen.

The most highly preferred constituents of the semibright additive of the types discussed above may be those which are compatible with bright nickel plating solutions. When semi-bright additives compatible with bright nickel plating solutions are employed, a duplex nickel plate including a plate of bright nickel plated above the semibright nickel plate obtained in accordance with the process of this invention may be obtained, without resort to an intermediate rinse. Typical aromatic aldehyde constituents which are compatible with bright nickel plating solutions include piperonal, benzaldehyde, terephthaldehyde, etc.

When the aromatic aldehyde which is used in combination with an aliphatic aldehyde as an additive composition for semi-bright nickel plating baths is piperonal or a piperonal derivative, the aromatic aldehyde may be characterized by the following formula:

wherein R may be hydrogen or an inert or non-reactive substituent. The piperonal additives which may be used according to this invention include piperonal se, or piperonal derivatives wherein the piperonal ring bears inert or non-reactive substituents in any of the 2,5 or 6 positions on the aromatic nucleus. In addition the heterocyclic ring which is bonded to the piperonal nucleus may bear one or two lower alkyl groups of from 1-4 carbon atoms. Typical inert or non-reactive substituents which may be bonded to the aromatic nucleus include hydrogen, alkyl, aryl cycloalkyl, aralkyl, alkaryl, alkenyl, ether, halogen, ester, etc. Typical specific substituents may be methyl, ethyl, propyl, phenyl, cyclopentyl, cyclohexyl, benzyl, tolyl, vinyl, propenyl, ethoxy, chloro, bromo, carboethoxy, etc. The preferred piperonal additive may be piperonal se. The piperonal additive may be particularly useful in contributing to leveling, refining grain size, promoting ductility, and reducing tensile stress.

Excellent semi-bright deposits may be obtained when the aromatic aldehyde additive is used in combination with an aliphatic aldehyde. The aliphatic aldehyde may be one wherein the aldehyde group -CHO is on a molecule which may be derived from an aliphatic hydrocarbon, and may be a hydrocarbon radical preferably selected from the group consisting of alkyl, alkenyl, cycloalkyl, including such radicals when inertly substituted. When R is alkyl, it may typically be straight chain alkyl or branched alkyl, including methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-amyl, neopentyl, isoamyl, n-hexyl, isohexyl, heptyls, octyls, decyls, dodecyls, tetradecyl, octadecyl, etc. Preferred alkyl includes lower alkyl i.e. having less than about carbon atoms i.e. octyls and lower. When R is alkenyl, it may typically be vinyl, allyl, l-propenyl, methallyl, buten-l-yl, buten-Z-yl, buten-3-yl, penten-l-yl, hexenyl, heptenyl, octenyl, decenyl, dodecenyl, tetradecenyl, octadecenyl, etc. When R is cycloalkyl, it may typically be cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, etc. R may be inertly substituted e.g. may bear a non-reactive substituent such as alkyl, cycloalkyl, alkenyl, ether, halogen, ester, etc. Typical substituted alkyls include 3-chloropropyl, 2-ethoxyethyl, carboethoxymethyl, etc. Substituted alkenyls include 4-chlorobutyl, chloroallyl, etc. Substituted cycloalkyls include 4-methylcyclohexyl, 4-chlorocyclohexyl, etc.

Typical aliphatic aldehydes may inclde formaldehyde (including paraformaledhyde), acetaldehyde, propionaldehyde, butyraldehyde, hexylaldehyde, etc. Other typical aliphatic aldehydes may include chloral (i.e. trichloroacetaldehyde), chloral hydrate, bromal (i.e. tribromacetadehyde), bromal hydrate, etc. The preferred aliphatic aldehyde may include formaldehyde, chloral, chloral hydrate, bromal, and bromal hydrate.

The combination of aromatic aldehyde and aliphatic aldehyde may be particularly useful in enhancing uniformity and promoting leveling of the semi-bright nickel deposits. The aliphatic aldehyde which is employed in combination with the aromatic aldehyde may be combined with the aromatic aldehyde as the pure compound, as a water-solution of the aliphatic aldehyde, or as compounds which release the aliphatic aldehyde, e.g. formaldehyde, under the conditions of the semi-bright nickel plating operation. For example, chloral hydrate may be used in combination with an aromatic aldehyde such as benzaldehyde, piperonal, or piperonal derivatives or polymers of formaldehyde such as paraformaldehyde may be employed in combination with aromatic aldehydes as described herein.

The preferred aromatic aldehydes and aliphatic aldehydes which may be employed may be those which are water-soluble i.e. soluble in the nickel plating solution (at the temperature of operation) in effective amount, typically at least about 0.01 g./l. of aldehyde.

The novel semi-bright compositions or additives of this invention may preferably be used in nickel plating baths maintained at an acid electrometric pH, such as those of Tables I-VII, typically the bath of Table I, in amounts each of at least 0.01 g./l. of plating bath, preferably 0.01-0.20 g./l. Lower concentrations may give appreciable grain refinement. The most preferred concentration may be from 0.02-0.06 g./l. of additive in the plating bath.

Typically there may be present a combined additive in the amount of 002-02 g./l. preferably at least 0.05 g./l. and typically 0.1 g./l. of plating bath which combined additive includes 0.025-0.l g./l., say, 0.050 g./l. of aromatic aldehyde and 0025-01 g./l., say, 0.050 g./l. of formaldehyde. The electrometric pH may typically be 2-5, preferably 3-4.

A particular feature of the novel semi-bright nickel baths of the invention is that the aldehydes, particularly the aliphatic aldehydes, may last for a relatively long period of time even 'when the semi-bright nickel bath is subjected to vigorous air agitation. Thus, the semi-bright nickel baths prepared according to the present invention may be replenished less frequently to compensate for additive consumption than other semi-bright nickel plating compositions. Furthermore, the use of the novel semibright nickel additive may result in relatively good coverage at low current densities.

A preferred nickel plating solution may be a mixed sulfate-sulfamate bath which is maintained at an electrometric pH of about 4.0 and which may contain g./l. of nickel sulfate heptahydrate, g./l. of nickel sulfamate, 45 g./1. of nickel chloride hexahydrate, 45 g./l. of boric acid, 0.05 g./l. of benzaldehyde and 0.05 'g./l. of formaldehyde. In this composition piperonal may be substituted for benzaldehyde. Thus a mixture of 0.05 g./l. of piperonal or a piperonal derivative in combination with 0.05 g./l. of formaldehyde may be used in the sulfatesulfamate bath.

The additive components may be added to nickel plating baths as individual components or may be dissolved to form separate stock solutions for convenience. Examples of such stock solutions may contain 20-50 g./l. of an aromatic aldehyde in an organic solvent such as isopropanol, or isopropanol-water. Suitable solutions of formaldehyde (35-40 percent by weight aqueous formaldehyde or suitable aqueous dilutions thereof) or solutions of paraformaldehyde in solvents such as Water, isopropanol, isopropanol-water etc. may be employed.

Semi-bright nickel plating in accordance with this invention may be carried out by immersing a basis metal cathode into a nickel plating bath as hereinbefore disclosed. The anode may be a soluble anode, typically a nickel metal, or an insoluble anode, typically lead. If nickel is used as the anode it is preferably sulfur-depolarized (SD) type of nickel. Plating may be carried out typically in chloride-containing baths for about 10-60 minutes, at 40-60 C., say 50 C., with mechanical or air agitation, the latter being preferred. The cathode current density may be typically 25-10 am-peres per square decimeter (a.s.d.), preferably 5 a.s.d.

In accordance with certain aspects of this invention, medium or very high speed deposition of semi-bright nickel may also be effected by a process comprising passing direct current from an anode to a metal cathode through an aqueous nickel plating solution including at least one nickel compound capable of providing nickel ions for electroplating nickel, an aromatic aldehyde, and an aliphatic aldehyde, maintaining the cathode current density during said plating at a level of at least 10 a.s.d.; and maintaining a high relative velocity between said nickel plating solution and said metal cathode thereby obtaining a semi-bright, rapidly deposited nickel plate.

The substantially non-polarizing anodes which may preferably be used in the very high or medium speed electroplating aspect of this invention may preferably be insoluble anodes, such as lead which have very little tendency to polarize, even at very high current density, or certain soluble anodes, such as the commercially available SD type of nickel which has less tendency to polarize than other soluble nickel anodes and may be used at relatively high current densities e.g. up to 40 a.s.d. The SD type of nickel is an electrolytic nickel containing a controlled amount of sulfur as nickel sulfide which is nickel bath insoluble. When an insoluble anode is used the bath typically should be chloride-free. Such a bath may be replenished in nickel metal content and have its pH adjusted by the addition of an alkaline oxide, hydroxide, or carbonate of nickel, preferably in a separate regenerating tank.

Thus, according to this high speed plating aspect of the invention, a current density of greater than about a.s.d., and preferably -60 a.s.d., may be used, although a current density of 120 a.s.d. or higher may be applied during electroplating of nickel, using baths containing the novel additives of the invention. Plating carried out in this manner may permit deposition of a predetermined thickness of semi-bright nickel in a time which is as little as 10% or less of the time required when ordinarily used plating conditions with soluble nickel anodes are used. Typically, production of a semibright nickel plate microns thick according to this aspect of the invention may require 3 minutes in contrast to minutes for typical prior art plating processes.

When medium or very high speed electroplating is desired, a high relative velocity may be maintained between the bath and the cathode. Typically the high relative velocity between the bath and the cathode is maintained at a level equivalent to 60-320, say 150 cm./secend. The agitation may be produced by vibration (including ultrasonic), rotation of the cathode relative to the solution, by pumping the electrolyte through the system and over the cathode surface, or by very vigorous and directional agitation of the electrolyte with appropriately positioned propellers or other devices, etc.

The novel process of this invention may permit attainment of l2.5-50 microns, say 25 microns, of semibright nickel plate characterized by its fine grain, high ductility, high gloss, uniform appearance, high covering power, and by its essentially sulfur-free character.

It is a particular feature of the novel semi-bright plate of this invention that, since it is deposited from a bath containing aldehydes with no sulfur contributing group in the molecule, it may be substantially sulfur-free and possess a high degree of ductility for a semi-bright plate.

The plating baths may also contain additional constituents such as anionic wetting agents to reduce any tendency toward hydrogen pitting. High foaming anionic wetting agents such as sodium lauryl sulfate may be used in conjunction with mechanical agitation; and low foaming anionic Wetting agents such as sodium dialkyl sulfosuccinates may be used with air agitation. Although these wetting agents may commonly contain sulfur, unexpectedly, no increase in the sulfur content of the de posits may be observed when they are used with the additives of this invention. The wetting agents may typically be present in amounts of 0.1-1 g./l. of plating solution.

It is a further feature of this invention that the novel semi-bright additive composition is completely compatible when used in combination with other semi-bright additives (including sulfur-containing compounds) to augment and extend advantageous features imparted by such other additives, including for example oxy-omega-sulfohydrocarbon-di-yl coumarins prepared by reacting in a solvent dispersion e.g. of methanol, a hydroxy coumarin, a compound of the formula MOH wherein M is a metal, and a hydrocarbon sultone or by reacting a hydroxy coumarin with a salt of a hydroxy hydrocarbon-di-yl sulfonate such as sodium isethionate.

Thus, semi-bright nickel plate obtained from a sulfamate plating bath having an electrometric pH of 4.0 containing 375 g./l. of nickel sulfamate, g./l. of nickel chloride, 45 g./l. of boric acid and 0.2 g./l. of potassium 7-oxy-omegasulfo-propyl coumarin in 10 minutes at 6 a.s.d. and 60 C., may be characterized as highly leveled, very fine grained, of low tensile stress, and very ductile. These characteristics may be increased even more if about 0.025 g./l. benzaldehyde, 0.025 g./l. piperonal, and 0.025 g./l. paraformaldehyde are added to the sulfamate plating bath.

The following examples are submitted for the purpose of illustration only and are not to be construed as limiting the scope of the invention in any way. The illustrative examples disclose semi-bright nickel plating baths containing the novel additives of this invention and electroplating processes wherein these baths are used.

EXAMPLE 1 1 liter of the following Watts-sulfamate bath may be prepared:

Nickel sulfate heptahydrate g./l Nickel sulfamate g./l Nickel chloride hexahydrate g./l 45 Boric acid g./l 45 pH electrometric 4.0

Water to 1 liter.

The bath may be thermostatically controlled at 60 C. and air-agitated. A single cotton cloth bagged SD nickel anode may be positioned in the bath. A highly polished brass strip 20 cm. x 2.5 cm. x 0.08 cm., pleated in 45 angles, may then be cleaned and immersed as the cathode in the bath except for the top 2.5 cm.

In a control run, a current of 5 amperes (average current density 5 a.s.d.) may be passed through the bath at 60 C. for 30 minutes to obtain a dull, grainy, non-uniform deposit.

In the practice of the invention, 0.050 g./l. piperonal and 0.050 g./l. of formaldehyde may then be added to the bath and the plating test repeated. This time a fine grained, very ductile deposit of high gloss and very uniform appearance may be obtained. This deposit may also be characterized as being relatively low in tensile stress and as being substantially free of sulfur, i.e. as containing less than 0.008% by weight of sulfur.

EXAMPLE 2 1 liter of the following Watts bath may be prepared:

Nickel sulfate heptahydrate g./l 300 Nickel chloride hexahydrate g./l 45 Boric acid g./l 45 pH electrometric 3.8

Water to 1 liter.

The bath may be thermostatically controlled at about 55 C. and air agitated, 0.050 g./l. of benzaldehyde and 0.050 g./l. of formaldehyde may be added to the bath and electroplating carried out at a current of about 5 amperes (average current density 5 a.s.d.) and 50 C. for about 30 minutes using a bagged SD nickel anode and a highly polished brass cathode strip, having the same dimensions as in Example 1, pleated in 45 angles. The semi-bright nickel deposit may be noted as being finely grained, very ductile, of relatively high gloss, of very uniform appearance, relatively low in tensile stress, and substantially free of sulfur.

EXAMPLE 3 1 liter of the following sulfamate bath may be prepared:

Nickel sulfamate g./l 375 Nickel chloride hexahydrate g./l 45 Boric acid g./l 45 pH electrometric 4.0

Water to 1 liter.

The bath may be thermostatically controlled at 55 C. 0.2 gram of potassium 7-oxy-omega-sulfo-propyl coumarin may be added to the bath and electroplating carried out at a current of 5 arnperes at 55 C. for 30 minutes using a bagged SD nickel anode and a highly polished brass cathode strip, having the same dimensions as in Example 1, pleated in 45 angles. The deposit obtained from this control run may be very fine grained, well-leveled, very ductile, and having a milky haze.

The above example may be modified to fall within the scope of this invention by the further addition to the bath of 0.025 g./l. benzaldehyde, 0.025 g./l. piperonal, and 0.025 g./l. of paraformaldehyde. The characteristics of the deposit obtained are augmented and extended beyond the characteristics of the semi-bright nickel deposit produced in the preceding portion of this Example 3. Thus, the semi-bright nickel deposit produced using a combination of benzaldehyde, piperonal, and paraformaldehyde as auxiliary additives may be noted as being more finely grained, ductile, well-leveled, and more glossy and with relatively low tensile stress.

EXAMPLE 4 1 liter of the following Watts-bath may be prepared:

Nickel sulfate heptahydrate g./l 375 Nickel chloride hexahydrate g./ L- 7.5 Boric acid g./l 45 pH electrometric 4.0

Water to 1 liter.

The bath may be thermostatically controlled at 54 C. and mechanically agitated with propellers. Then 0.025 g./l. cinnamaldehyde, 0.035 g./l. formaldehyde, and 0.5 g./l. sodium lauryl sulfate wetting agent may be added to the bath and electroplating carried out at a current of 5 amperes (average current density of 3.6 a.s.d.) at 54 C. for 30 minutes using a bagged SD nickel anode and a copper plated zinc base die-cast handle having a surface area of about 160 sq. cm. which may be scribed with a single pass of a 1.2 cm. wide zero-grit emery paper. Within minutes a semi-bright deposit may be obtained of remarkably high luster, uniformity, and fine grain size wherein the scratched band may be virtually completely filled in, indicating good leveling.

EXAMPLE 5 1 liter of the following Watts bath may be prepared:

Nickel sulfate heptahydrate g./l 300 Nickel chloride hexahydrate g./l 45 Boric acid g./l 45 pH electrometric 4.0

Water to 1 liter.

The bath may be thermostatically controlled at 60 C. and mechanically agitated with propellers. Then 0.050 g./l. terephthaldehyde, and 0.030 g./l. of formaldehyde in combination with 0.5 g./l. of a high foaming wetting agent (sodium lauryl sulfate) may be added to the bath. Electroplating may be carried out at a current of 5 a.s.d. at 60 C. for 30 minutes using a bagged SD nickel anode and a highly polished brass cathode strip, having the same dimensions as in Example 1, pleated in 45 angles. The deposit obtained with the additive ingredients terephthaldehyde and formaldehyde is much improved and may be characterized as being more fine-grained, better leveled, and more uniform in appearance, than the nonuniform grainy nickel deposit which is obtained without the combination of aromatic aldehyde and formaldehyde. With the additive combination the tensile stress was not excessively increased and the deposit was substantially free of sulfur. the semi-bright nickel deposit obtained by the use of these additives may permit a more rapid buildup of luster when the semi-bright nickel plated article is subsequently given a deposit of bright nickel plate.

EXAMPLE 6 1 liter of the following Watts bath may be prepared:

Nickel sulfate heptahydrate g./l 300 Nickel chloride hexahydrate g./l 45 Boric acid g./l 45 pH electrometric 3.8

Water to 1 liter.

The bath may be thermostatically controlled at 55 C. and air agitated. Then 0.050 g./ 1. piperonal and 0.025 g./ 1. chloral hydrate may be added to the bath and electroplating carried out at a current of 5 amperes (average current density of 5 a.s.d.) and at 55 C. for 30 minutes used a bagged SD nickel anode and a highly polished brass cathode strip, having the same dimensions as in Example 1, pleated in 45 angles. The semi-bright nickel deposit obtained may be noted as being finely grained, very ductile, of high gloss, of very uniform appearance, relatively low in tensile stress, and substantially free of sulfur.

EXAMPLE 7 One liter of the following Watts bath may be prepared:

Nickel sulfate heptahydrate g./l 300 Nickel chloride hexahydrate g./1 45 Boric acid g./l 45 pH electrometric 3.8

Water to 1 liter.

The bath may be thermostatically controlled at 55 C. and air agitated. Then 0.050 g./l. of 'benzaldehyde and 0.025 g./l. of bromal hydrate may be mixed into the bath and electroplating carried out at a current of 5 amperes (average current density of 5 a.s.d.) at 55 C. for 30 minutes using a bagged SD nickel anode and a highly polished brass cathode strip, having the same dimensions as in Example 1, pleated in 45 angles. The semi-bright nickel deposit obtained may 'be noted as being finely grained, very ductile, of high gloss, of very uniform appearance, relatively low in tensile stress, and substantially free of sulfur.

EXAMPLE 8 Control example One liter of the following Watts bath may be prepared:

Nickel sulfate heptahydrate g./l 300 Nickel chloride hexahydrate g./l 45 Boric acid g./1 45 pH electrometric 3.8

Water to 1 liter.

The bath may be thermostatically controlled at 55 C. and air agitated. Then 0.15 g./l. of formaldehyde may be mixed into the bath and electroplating carried out at a current of 5 amperes (average current density of 5 a.s.d.) at 55 C. for 30 minutes using a bagged SD nickel anode and a highly polished brass cathode strip, having the same dimensions as in Example 1, pleated in 45 angles. A fine grain deposit may 'be obtained, but a microstriated deposit may be seen at the low (i.e. less than about 0.5 a.s.d.) current density range. The presence of such a microstriated deposit may be objectionable because such diiferences may not be covered or masked by a subsequent bright nickel deposit.

EXAMPLE 9 Using a bath identical to that of Example 8 but substituting a combination of 0.08 g./ 1. of formaldehyde and 0.05 g./l. of piperonal in place of the 0.15 g./l. of formaldehyde and electroplating using exactly the same conditions as in Example 8 may give a deposit which is uniformly glossy in the low current density range without the formation of any microstriations.

EXAMPLE 10 One liter of the following Watts bath may be prepared:

Nickel sulfate heptahydrate g./l 300 Nickel chloride hexahydrate g./l Boric acid ..g./1 45 pH electrometric 4.0

Water to 1 liter.

The bath may be thermostatically controlled at 65 C. The solution may be passed through a conduit obliquely onto one end of the surface of a vertically positioned brass electrode with the section to be plated 13.5 cm. long and 1.0 cm. wide, to give an exposed cathode area of 25.7 cm. On the front of this highly polished brass cathode there may be inscribed a longitudinal 1 cm. wide single pass of zero-grit emery scratches centrally positioned on the cathode surface. The back of the cathode may be sealed by means of a plastic backing. The velocity of the impinging stream may be about 150 cm./second. The angle of the downwardly flowing stream may be 45 to the Vertical.

The outer periphery of the cathode may be bounded by plastic barriers or shields extending outwardly from the cathode thereby effecting channelling of the electrolyte as it passes over the cathode. This entire assembly may be submerged in a body of electrolyte. Cathode contact may be made to that section of the strip, not to be pleated, which extends out of the solution. A slab of SD nickel may be positioned parallel to the cathode at a distance of 20 cm. The times of plating used may be 3 minutes to give a deposit thickness of one mil. A semibright fine grained deposit of nickel with good ductility and leveling Was obtained.

It will be apparent that this invention has been described with respect to specific examples and various modifications will be apparent to those skilled-in-the-art.

I claim:

1. A process of electrodepositing a semi-bright nickel deposit which comprises passing a current from an anode to a metal cathode in an aqueous acidic nickel plating solution containing at least one nickel compound providing nickel ions for electrodepositing nickel and including as semi-bright additive an aromatic aldehyde in combination with an aliphatic aldehyde in said aqueous acidic nickel plating solution.

2. A process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 wherein said aromatic aldehyde and said aliphatic aldehyde are each soluble in said solution to the extent of at least 0.010 g./l.

3. The process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 wherein said semi-bright additive includes 0.01 g./l.0.2 g./l. of said aromatic aldehyde and 0.01 g./l.0.2. g./l. of said aliphatic aldehyde.

4. A process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 wherein oXy-omega-sulfohydrocarbon-di-yl coumarin semi-bright additive also is present in said nickel plating solution.

5. The process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 wherein said aromatic aldehyde is of the formula:

(IJHO wherein at least one R is selected from the group consisting of hydrogen, alkyl, aryl, cycloalkyl, aralkyl, alkaryl, alkenyl, ether, halogen, and ester.

6. The process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 which comprises passing direct current from an anode to a metal cathode through an aqueous nickel plating solution including at least one nickel compound capable of providing nickel ions for electroplating nickel and including as semi-bright additive an aromatic aldehyde soluble to the extent of at least 0.010 g./l. in said solution and wherein said aliphatic aldehyde contains 1-10 carbon atoms.

7. The process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 which comprises passing direct current from anode to a metal cathode through an aqueous nickel plating solution including at least one nickel compound capable of providing nickel ions for electroplating nickel and including as semi-bright additive an aromatic aldehyde soluble to the extent of at least 0.010 g./l. in said solution and at least one compound selected from the group consisting of formaldehyde, paraformaldehyde, chloral, chloral hydrate, bromal, and bromal hydrate.

8. A process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 wherein at least one aromatic aldehyde is selected from the group consisting of benzaldehyde, cinnamaldehyde, piperonal, and terephthaldehyde.

9. A process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 wherein the aromatic aldehyde is a piperonal derivative.

10. A process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 wherein the aromatic aldehyde is piperonal.

11. A process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 wherein the aromatic aldehyde is a cinnamaldehyde derivative.

12. A process for electrodepositing a semi-bright nickel deposit as claimed in claim 1 wherein the aromatic aldehyde is cinnamaldehyde.

13. A process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 wherein at least one aromatic aldehyde is terephthaldehyde.

14. The process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 which comprises passing direct current from an anode to a metal cathode through an aqueous nickel plating solution including at least one nickel compound capable of providing nickel ions for electroplating nickel and including as semi-bright additive piperonal and formaldehyde.

15. The process of electrodepositing a semi-bright nickel deposit as claimed in claim 1 which comprises passing direct current from an anode to a metal cathode through an aqueous nickel plating solution including at least one nickel compound capable of providing nickel ions for electroplating nickel and including as semi-bright additive benzaldehyde and formaldehyde.

16. A semi-bright nickel plating solution comprising an acidic aqueous nickel plating solution including at least one nickel compound capable of providing nickel ions for electrodeposition of nickel on a basis metal cathode and including as semi-bright additive an aromatic aldehyde and an aliphatic aldehyde.

17. A nickel plating solution as claimed in claim 16 comprising an acidic aqueous nickel plating solution of at least one nickel compound capable of providing nickel ions for electrodeposition of nickel on a basis metal cathode wherein said aromatic aldehyde and an aliphatic aldehyde are each soluble in said solution to the extent of at least 0.010 g./l.

18. A nickel plating solution as claimed in claim 16 comprising an acidic aqueous nickel plating solution of at least one nickel compound capable of providing nickel ions for electrodeposition of nickel on a basis metal cathode wherein said semi-bright additive includes 0.01 g./l. 0.2 g./ 1. of said water-soluble aromatic aldehyde and 0.01 g./l.0.2 g./l. of aliphatic aldehyde.

19. A nickel plating solution as claimed in claim 16 comprising an acidic aqueous nickel plating solution of at least one nickel compound capable of providing nickel ions for electro-deposition of nickel on a basis metal cathode wherein oxy-omega-sulfohydrocarbon-di-yl coumarin semi-bright additive is present in said nickel plating solution.

20. A nickel plating solution as claimed in claim 16 comprising an acidic aqueous nickel plating solution of atleast one nickel compound capable of providing nickel wherein at least one R is selected from the group consisting of hydrogen, alkyl, aryl, cycloalkyl, aralkyl, alkaryl, alkenyl, ether, halogen, and ester.

21. A nickel plating solution as claimed in claim 16 comprising an acidic aqueous nickel plating solution of at least one nickel compound capable of providing nickel ions for electrodeposition of nickel on a basis metal cathode which includes as semi-bright additive an aromatic aldehyde soluble to the extent of at least 0.010 g./'l. in said solution and at least one compound selected from the group consisting of formaldehyde, paraformaldehyde, chloral, chloral hydrate, bromal, and bromal hydrate.

22. A nickel plating solution as claimed in claim 16 comprising an acidic aqueous nickel plating solution of at least one. nickel compound capable of providing nickel ions for electrodeposition of nickel on a basis metal cathode wherein at least one aromatic aldehyde is selected from the group consisting of benzaldehyde, cinnamaldehyde, piperonal, and terephthaldehyde.

23. A nickel plating solution as claimed in claim 16 comprising an acidic aqueous nickel plating solution of at least one nickel compound capable of providing nickel ions for electrodeposi'tion of nickel on a basis metal cathode wherein the aromatic aldehyde is a piperonal derivative.

24. A nickel plating solution as claimed in claim 16 comprising an acidic aqueous nickel plating solution of at least one nickel compound capable of providing nickel ions for electrodeposition of nickel on a basis metal cathode wherein the aromatic aldehyde is piperonal.

25. A nickel plating solution as claimed in claim 16 comprising an acidic aqueous nickel plating solution of at least one nickel compound capable of providing nickel ions for electrodeposition of nickel on a basis metal cathode wherein the aromatic aldehyde is a cinnamaldehyde derivative.

26. A nickel plating solution as claimed in claim 16 comprising an acidic aqueous nickel plating solution of at least one nickel compound capable of providing nickel ions for electrodeposition of nickel on a basis metal cathode wherein the aromatic aldehyde is cinnamaldehyde.

27. A nickel plating solution as claimed in claim 16 comprising an acidic aqueous nickel plating solution of at least one nickel compound capable of providing nickel ions for electrodeposition of nickel on a basis metal cathode wherein at least one aromatic aldehyde is terephthaldehyde.

28. A semi-bright nickel plated article wherein the semi-bright nickel deposit is prepared by passing current from an anode to a metal cathode through an aqueous acidic nickel plating solution containing at least one nickel compound providing nickel ions for electroplating nickel and including as semi-bright additive an aromatic aldehyde and an aliphatic aldehyde.

29. A high speed process of electrodepositing a semibright nickel deposit which comprises passing a current from an anode to a metal cathode. in an aqueous acidic nickel plating solution containing at least one nickel compound providing nickel ions for electrodepositing nickel at a plating current density of at least about 10 amperes per square decimeter and including as semibright additive an aromatic aldehyde in combination with an aliphatic aldehyde in said aqueous acidic nickel plating solution.

30. A high speed process of electrodepositing a semibright nickel deposit as claimed in claim 29 wherein the plating current density is 10-120 amperes per square decimeter.

31. A high speed process of electrodepositing a semibright nickel deposit as claimed in claim 29 wherein the plating current density is 20-60 amperes per square decimeter.

References Cited UNITED STATES PATENTS 2,085,754 7/1937 Hull 20449 2,795,540 6/1957 Brown 20449 FOREIGN PATENTS 525,848 9/1940 Great Britain.

476,452 8/1951 Canada.

DANIEL E. WYMAN, Primary Examiner C. F. DEES, Assistant Examiner 

